1. Field of the Invention
The present invention relates to a character reading system which can read only characters from an object to be read, for instance as a preliminary process in character recognition.
2. Description of the Related Art
A high degree of reading technology is required in optical character readers when the recording on the object to be read, which becomes the subject for reading, is in an arbitrary format. Therefore, in conventional optical character readers, the objects to be read were prepared by providing entry frames for restricting the entry positions of characters, etc.
Normally, the entry frame on the object to be read is not required in the character recognition stage. For this reason, it is printed in a special color so that it is easy to drop out or erase. However, the choice of this color is limited, there is a limit to the colors which can be used for the entry frames.
Therefore, as means of enabling the extension of the limits to colorings for entry frames, various systems have been proposed, as disclosed in, for instance, Japanese Laid-Open Patent No. Showa 57-143683 and Japanese Patent Application No. Heisei 2-254308.
However, these are for dropping out entry frames in monochrome. It is difficult to drop out the entry frames in the cases of objects to be read with entry frames in two or more colorings. In particular, with the system where an optical filter is used, this system is at a disadvantage where the coloring is faint in the colored object.
The technology for the extraction of the serial number overprinted on the pattern on valuable securities such as banknotes is known, for example Japanese Laid-Open Patent No. Heisei 3-191482 and Japanese Laid-Open Patent No. Heisei 2-73476. In the former system, the color information is used to extract a specified color, this can be used for an object which is a pattern of two or more types of coloring, but the extraction output (character separation by color information) is a binary image. Compared with this, in the latter system, the character including variable density information can be extracted but this is for objects which are patterns of one type of coloring (monochrome).
For example, as technology for extracting the postal code from mail containing the entry frame and the special delivery stamp or indicia thereon, the former system (Japanese Laid-Open Patent No. Heisei 3-191482) is useful. However, this system has disadvantages that, as the extraction output is a binary image, blurred postal codes are extracted and the special delivery stamp etc. having variable density information cannot be completely dropped out.
The problem with prior art such as the above-mentioned, is that where there are two or more types of colorings in the information to be dropped out from the object, this dropping out cannot be done with accuracy.
As described above, in conventional optical character readers, there was the disadvantage of not being able to drop out the entry frames in objects to be read with entry frames of two or more colorings.